1. Technical Field
This invention relates generally to silicon-substituted fullerene compounds and methods of making them.
2. Background Art
Fullerenes are a recently discovered form of pure solid carbon. They are cage-like hollow structures comprised of hexagon and pentagon rings fused together to form ball shaped hollow molecules which resemble geodesic domes. Fullerenes may range from 32 carbons up to many hundreds of carbon atoms. A fullerene molecule containing 60 carbons (C.sub.60) is the archetype, and is known as Buckminsterfullerene. For a general discussion of fullerenes, see R. Curl, et al., Scientific American, 54-63 (October 1991). The disclosure of this articles, and of all other articles referred to herein, are incorporated by reference as if fully set forth herein.
Fullerenes have been synthesized by decomposing graphite rods in the presence of helium. Graphite rod decomposition may be accomplished by electric arc, as discussed in A. Koch, et al., 56 Journal of Organic Chemistry, 4543-4545 (1991)(C.sub.60 ; C.sub.70), or by plasma discharge as discussed in D. Parker; et al., 113 Journal American Chemical Society, 7499-7503 (1991)(C.sub.60 -C.sub.266).
Researchers have identified many interesting uses of fullerenes over the past few years. For example, fullerenes show promise for use in diamond films, nonlinear optical and superconducting materials, semiconductors, and photo-conductors. Because pure fullerenes form discreet crystals, more processable forms of fullerenes are needed to more fully exploit their unique properties.
A few polymers of fullerenes have been synthesized to help meet this need. In this regard, D. Loy, et al. synthesized a C.sub.60 -p-xylyene copolymer. See, 114 Journal American Chemical Society, 3977-3978 (1992). Another example is a palladium polymer of a Buckminsterfullerene synthesized by H. Nagashima, et al., Journal of the Chemical Society, "Chemical Communications", 377-379 (1992). Other examples are the synthesis by S. Shi, et al. of a polyester and polyurethane of diphenyl C.sub.61. (See, 114 Journal American Chemical Society, 10656-10657 (1992)) and a polymer-substituted fullerene shown in E. Samulski, et al., 4 Chemical Materials, 1153-1157 (1992).
A drawback of some of the foregoing substituted fullerenes is that they employ expensive reagents, like palladium and xylylene. Further, some are made from reagents which have toxic side effects. Accordingly, there is a need for an inexpensive and non-toxic polymeric substituted fullerene.